Sphygmomanometer cuffs for non-invasive or bloodless blood pressure measurement are known from practice. They usually have an elongated, rectangular cuff, which is placed around the upper arm, thigh or another body part of a patient in a ring-shaped pattern for measuring the patient's blood pressure and contain a rectangular inflatable cuff part. This inflatable cuff part may be filled with a fluid—usually air or gas—and presses a blood vessel located within the body part surrounded by the cuff, usually an artery, such that the flow sounds generated in the blood vessel due to the pressure applied to it make it possible to measure the blood pressure according to Riva-Rocci.
To determine the blood pressure as correctly as possible by means of a sphygmomanometer cuff as described above, special attention must be paid to ensure that the height of the inflatable cuff part over the blood vessel (i.e., the extension of the inflatable cuff part in the direction of blood flow in the blood vessel to which pressure is being applied by the inflatable cuff part) be equal to about 40% of the circumference of the body part on which the blood pressure measurement is being carried out. In case of blood pressure measurement on the upper arm of a patient, the inflatable cuff part extending in the longitudinal direction of the upper arm should therefore have a width or height that corresponds to 40% of the circumference of the upper arm.
Since there may be substantial differences among patients in terms of the circumference of their upper arm—as well as other body parts used for blood pressure measurement, and any other body part suitable for blood pressure measurement will also be meant therefore when referring to the upper arm below according to the present invention—various sizes of sphygmomanometer cuffs are available in specialist shops, as they are also disclosed, for example, in the German Patent Application DE 195 02 573 A1.
The circumference of, for example, the upper arm is often estimated only too approximately for selecting the corresponding size of cuff in the routine practice of blood pressure measurements. However, the incorrect cuff size selected on the basis of this erroneous estimation regularly leads to considerable errors of measurement, which has meanwhile been able to be demonstrated by a large number of studies. In the case in which the cuff selected is too small, so that the area over which the force acts due to the inflated inflatable cuff part is too small, the measured blood pressure is consequently incorrectly too high. If an excessively large cuff is used, whose force acts along an excessively large section of the artery, the measured blood pressure is consequently incorrectly too low. Even small deviations from the intended 40% of the circumference in selecting the sphygmomanometer cuff to be used may lead to considerable deviations of the measured blood pressure values. For example, a measured blood pressure that is too low by 10% can be seen, for example, in case of a sphygmomanometer cuff that has a width or height corresponding to a full 50% of the circumference of the upper arm instead of the desired 40%. Likewise, a sphygmomanometer cuff inflatable cuff part whose width or height is only 20% of the circumference of the upper arm leads to a measured blood pressure that is too high by 20%.
However, experience has shown that such errors of measurement also occur during the determination of the blood pressure when the actual upper arm circumference is known but the correct sphygmomanometer cuff was not available for the blood pressure measurement. Experience has shown that the blood pressure measurement is carried out in such cases with cuffs of an incorrect size that do not fit optimally.
Measurement of the blood pressure on the upper arm, for which the circumference of the upper arm is used to determine the suitable width or height of the inflatable cuff part, may lead to incorrect measurements as well. The applicant was able to determine that the “40% of the upper arm circumference” rule as an indicator for the height or width of the inflatable cuff part of the sphygmomanometer cuff does not lead to reliable measurement results for all patients. The correctly determined blood pressure consequently depends on the size of the sphygmomanometer cuff for the patient.
The sphygmomanometer cuffs known commercially, such as those known from DE 195 02 573 A1, are usually manufactured from a rectangular piece of fabric, which is coated with PU or PVC. This piece of material is cut to twice the size the finished cuff has during use and subsequently reduced by half by simple folding in one direction. The three open cuff edges formed as a result are sealed, and the inflatable cuff part is manufactured in the same step. The drawback of the manufacture of conventional sphygmomanometer cuffs as described above is that a needlessly large amount of coated material is used, which leads to higher costs than necessary.